Anion-Dependent Synthesis of Cu(II) Complexes with 2-(1H-Tetrazol-5-yl)-1H-indole: Synthesis, X-Ray Structures, and Radical Scavenging Activity

Two mononuclear Cu(II) complexes, [Cu(phen)(2)(HL)]ClO(4)·H(2)O·2DMF (1) and [Cu(phen)(2)(HL)(2)]·EtOH (2), comprising 1,10-phentantroline (phen) and 2-(1H-tetrazol-5-yl)-1H-indole ligand (H(2)L) ligands are reported. Analysis and characterization of the samples were performed using standard physicochemical techniques, elemental analysis, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and UV-vis spectroscopy. Single-crystal X-ray crystallography revealed the formation of a pentacoordinate complex in 1 and a hexacoordinate complex in 2, in which the anionic ligand HL(−) has undergone monodentate coordination through the tetrazole unit. Furthermore, the crystal structure of H(2)L·MeOH is also discussed. The potential application of compounds 1 and 2 in bioinorganic chemistry was addressed by investigating their radical scavenging activity with the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and the results were supported also by theoretical calculations.